The Burj dwarfs the previous titleholder for world's tallest building -- the Taipei 101 in Taiwan, at 1,670 feet tall, with 101 stories.

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The Burj Dubai, designed by Chicago architects, surges past that with 160 stories. And at a reported 2,600 feet, it's nearly 1,000 feet taller than the Taipei 101 -- a difference the size of the Eiffel Tower. All told, the Burj Dubai is taller than two Empire State Buildings stacked together.

The building will house 5 million square feet of office space, a 175-room Armani hotel, 900 apartments, four swimming pools and the world's highest observation deck.

The official height — still a secret now — has been increased more than once during construction, which began in September 2004.

"A lot [of] people around the world want to build another [taller] building. So I thought, let's just keep this quiet as long as we can, " said Mohammed bin Ali Al Abbar, CEO of Emaar Properties, the building's developer.

The tower is engineered with a six-sided central core to minimize the forces of wind -- a critical factor on such a tall building. Still, engineers say the Burj will sway more than four feet at the top.

More than 10,000 workers have logged more than 29 million hours constructing the building.

But it took "Good Morning America" just 15 minutes to get to the top -- an astounding half-mile into the sky.

Ali Al Abbar said the Burj Dubai isn't just about being the tallest, but a symbol of
the "new Middle East," and the large-scale ambitions and opportunities of the multinational city of Dubai.